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Holography under extreme conditions

Periodic Reporting for period 1 - ExHolo (Holography under extreme conditions)

Reporting period: 2020-09-01 to 2022-08-31

Fundamental research let to the formulation of the theory of Quantum Chromo-Dynamics (QCD). QCD describes how the strong interaction mediates the exchange of particles. Via the experiments of the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Lab and of the Large Hadron Collider (LHC) at CERN one gets access to the relevant energy scales of the fundamental particles, the quarks and gluons, which are governed by QCD. The program of colliding heavy nuclei at ultra-relativistic speeds allows to gain insight on extreme matter under high temperatures and high pressures. This pushes humanities understanding of the constituents of the nuclei. In consequence this has a broad connection to a variety of fields, including astrophysics, neutrino physics and nuclear physics. This allows in consequence to get insights on the fundamental questions: how did the creation of matter in our universe happen after the big bang? how are the heavy nuclei composed and shaped? how do the high energy cosmic rays interact with our atmosphere and how does matter in compact stars behave? In particular this project aimed on providing new insights of extreme matter subject to high temperatures or high pressures. For the RHIC scan of the QCD phase diagram the project newly assessed various unstable first order phase transitions. With the heavy-ion theory group and a junior faculty ALICE experimentalist we studied the impact of the plasma on charm jets: The results we find are highly exciting as we predict a significant enhancement in jet chemistry for charm and anti-charm pair creation. This is a strong motivation for future high luminosity heavy-ion runs at the LHC.
New key scientific insights I have obtained during my fellowship at the Department of Theoretical Physics at the European Organisation for Nuclear Research (CERN TH) , where I held the ExHolo EU Horizon 2020 Marie Skłodowska-Curie Acton (MSCA) Individual Fellowship include:

A) first simulations of the spinodal instability with different first order phase transition near and far from a critical point

B) extraction of the formation timescales of the spinodal instability with varying degree of criticality

C) confirmation of a universal final inhomogeneous state across all different 1st order phase transitions

D) significant modification of the gluon to charm and anti-charm pair splitting inside of the quark-gluon plasma versus in the vacuum

E) identification of a new observable for the future high-luminosity collisions at the ALICE, CMS or ATLAS experiments of the Large Hadron Collider

These results were presented at key peer-reviewed international conferences and topical workshops. To enhance the transfer of knowledge to the larger scientific community and to the general public I actively tweet on twitter about the ongoing research at the CERN TH. I have in total over 2000 scientific tweets so far and > 500 community followers on the twitter handle @thermalization ( twitter.com/thermalization ).
Scientific progress happens because of new impactful discoveries. All results from this project are beyond state of the art. In addition they involve new phenomenological insights. The results of the calculations and numerical simulations reveal possible new directions for the ultra-relativistic experiments both at RHIC and at LHC. One major findings, is that the formation time of the spinodal instability is significantly faster away from a critical point, which should help for experimental discovery of the supposed first-order phase transition at RHIC. With my collaborators in the theory department at CERN we proposed a new observable for heavy ion collisions at CERN which is a key argument for the development of the future new generation detector ALICE 3 at the Large Hadron Collider. This future detector will be able to test our proposal. This leads to better understanding of the quark-gluon plasma and gives access to further investigations of the substructure components with medium modification. Moreover the newly discovered geometrical medium enhancement of the gluon to charm plus anti-charm pair will be incorporated in the cutting edge Monte-Carlo algorithms describing the jet evolution in medium.
The fraction of jets that carry a medium enhancement of this splitting.
llustration of a parton shower containing a gluon to charm and anti-charm splitting.
Evolution of a first order phase transition with the spinodal instability